Rotary solenoid shutter drive assembly and rotary inertia damper and stop plate assembly

ABSTRACT

A camera shutter assembly having a pair of superposed opaque planar shutter blades, each having an aperture and being arranged for reciprocal linear movement is disclosed. A pair of rotary solenoids, each connected to one of the blades by a linkage and arranged to be actuated separately at a predetermined interval is provided. An inertia damper and stop plate is built into each solenoid to prevent rebound.

United States Patent 1 [111 3,804,506 Fletcher et a1. Apr. 16, 1974 [54]ROTARY SOLENOID SHUTTER DRIVE 3,726,199 4/1973 Alfredsson et al. 95/53EA ASSEMBLY AND ROTARY INERTIA 3,724,350 4/1973 Mielke 95/53 E DAMPERAND STOP PLATE ASSEMBLY 3,176,170 3/1965 Fulton et a1. 95/55 X 3,381,5975/1968 Morton 95/55 [76] Inventors: James C. Fletcher, Administrator of,4 11/1 61 Takahama 95/55 X the National Aeronautics and Space EggenAdministration with respect to an 3,664,251 5/1972 Vincent 95/53 Einvention of; Walter L. Cable, Freehold Harold Primary Examiner.losephF. Peters, Jr. Daugherty, gightstownt N Attorney, Agent, or Firm-R. F.Kempf; J. R. Manning; J. H. Warden [22] Filed: May 21, 1973 [21] Appl.No.: 361,906 [57] ABSTRACT A camera shutter assembly having a pair ofsuper- [52] us. Cl. 354/234, 95/53 EA, 350/269 p s p q p n shutter a aavi g an [51] Int. Cl. G03b 9/16,G03b 9/42 p r n ng arr nged forreciprocal linear [58] Field of Search 95/53 E, 53 BA, 55; movement isdisclosed- A p of ry solenoids,

350/269, 272; 335/219, 272 each connected to one of the blades by alinkage and arranged to be actuated separately at a predetermined,

[56] References Cit d interval is provided. An inertia damper andstopplate UNITED STATES PATENTS is built into each solenoid to preventrebound.

2,909,978 10/ 1959 Fischer et a1. 95/55 X 6 Claims, 12 Drawing FiguresPATENFEHAPR 16 m4 SHEEV 2 SF 4 PATENTEIMPR 16 m4 SHEET 3 BF 4 PATENTEHAPR 1 6 1974 SHEET M- UF &

ROTARY SOLENOID SHUTTER DRIVE ASSEMBLY AND ROTARY INERTIA DAMPER ANDSTOP PLATE ASSEMBLY ORIGIN OF THE INVENTION The invention describedherein was made in the performance of work under a NASA contract and issubject to the provisions of Section 305 of the National Aeronautics andSpace Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

BACKGROUND OF THE INVENTION This invention generally relates to cameras,and more particularly, this invention relates to a camera shutter havinglong life and extreme accuracy.

Various types of cameras and camera shutters have been developed overmany years, each type being suitable for a particular need andenvironment. While a generalization can be made that all cameras, forpractical purposes, include a lens or other optical system for focusingan image, a shutter for controlling the exposure, and some means forrecording the image, such means being either a light-sensitivephotographic film or electronic apparatus, it is also clear that theseelements vary widely according to. the ultimate purpose for which thecamera will be used.

It is apparent that for use in a satellite a camera must be able tooperate ,under a wide variety of conditions and must be able towithstand extremes of temperature and mechanical abuse. For example, atthe time of launching the sate lite the camera will be subjected toforces many times that of gravity and, once the satelite is in orbit,the camera will be.operating essentially in a vacuum and at widetemperature extremes. Thus, it will be appreciated that such a cameramust be. designed to withstand these various types of abuse and to beextremely reliable due to the impossibilityto effect repairs andadjustments. In such a camera various conventional electronic means forrecording an image and, eventually, transmitting the same to earth areavailable. Similarly, lens systems which are capable of withstanding theextremes of shock and temperature are also available. The most delicateand, therefore, difficult to construct, is the shutter system. Such ashutter system must be capable of providing an extremely small exposuretime (from about 4 to about 16 milliseconds) at small tolerances 0.4milliseconds) and have an extremely long endurance life.

SUMMARY OF THE INVENTION It is, therefore a primary object of thepresent invention to provide a camera shutter for extremely shortexposure times and having a long endurance life.

It is another primary object of the present invention to provide acamera shutter having extreme accuracy and a low level of shock at theend of a blade stroke.

It is another object of the present invention to provide a simplyconstructed camera shutter having a double blade system combined withrotary solenoids having an inertia damper assembly.

It is still another object of the present invention, consistent with theforegoing objects, to provide a camera capable of withstanding extre'mesof shock and temperature.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects will becomeapparent as the description of the invention proceeds, such descriptionmaking reference to the annexed drawings wherein:

FIG. 1 is a front elevational view of the shutter assembly of theinstant invention with the shutter blades in the cocked position;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a vertical elevational view of the apparatus of FIG. Iillustrating the start of a shutter opening operation;

FIG. 4 is a plan view of the direct blade of the apparatus of FIG. ll;

FIG. 5 is a plan view of the indirect blade of the apparatus of FIG. 1;

FIG. 6 is a plan view of the apparatus of FIG. 1;

FIG. 7 is a sectional view taken on the line 7-7 of FIG. 1;

FIG. 8 is a schematic elevational view of the camera assembly accordingto the instant invention;

FIG. 9 is a partially sectional elevational view of the solenoid used inthe shutter of the instant invention;

FIG. 10 is a sectional view taken on the line 10-10 of FIG. 9; I i

FIG. 11 is a partially fragmented, partially sectional view of thesolenoid of FIG. 9 and;

FIG. 12 is an exploded view of the solenoid used in the shutter of theinstant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 fora basic understanding of the instant invention, there will be seen acamera shutter generally designated by the numeral 10, such shuttergenerally having a T-shaped frame 12 which includes a pair of rails 14each bearing a solenoid assembly 16, 17. A set of gibs 18 are provided.to guide the two shutter blades. The shutter blades consist of a directblade 20 and an indirect blade 22. Frame 12 also includes, between thegibs 18, an aperture 24. Direct blade 20 has an aperture 26 and directblade 22 has an aperture 28. A foot 30 is provided for aligning theshutter assembly in the camera. Direct shutter blade 20 is driven bysolenoid 17 by linkage means generally comprising arm 32 and link 34(FIG. 3) connected at the pivot points by bushings 36 and 38made of anysuitable material such as Delrin. Similarly, indirect blade 22 is drivenby solenoid 16 through arm 40 and link 42with bushings 44 and 46provided at the pivot points.

Turning momentarily to FIGS. 4 and 5, it will be seen that direct blade20 has an aperture 26 in the upper portion thereof while indirect blade22 has aperture 28 in the lower portion thereof. Returning to FIGS. 1and 2, it will be seen that both direct blade 20and indirect blade 22are in the deenergized, or cocked position. In this position, aperture24 is blocked. As will be described in more detail hereinbelow, to makean exposure, the direct solenoid 17 is actuated thereby moving thedirect blade 20 downwardly and aligning aperture 26 with aperture 24.After a pre-determined interval, indirect solenoid 16 is actuatedthereby moving indirect blade 22 downwardly and beginning to close theaperture. FIG. 3 shows the relationship of the blades 20 and 22 part-waythrough the exposure when direct blade 20 has moved downwardly to exposepart of aperture 24 and indirect blade 22 has not yet begun its travel.

Certain aspects of the operation of shutter assembly will be clarifiedby referring to FIGS. 6 and 7 wherein it will be seen that solenoids l6and 17 are mounted on opposite sides of frame 12. Arm 40 is so]- idlyfastened to output shaft 48 at 50 by any suitable means known in theart. Similarly, arm 32 is solidly fastened to output shaft 52 ofsolenoid 17 at 54 by suitable means. Direct blade and indirect blade 22are guided in their linear movement by channels 56 and 58, respectivelyin gibs l8.

Attention is now drawn to FIG. 8 which depicts shutter assembly 10 inplace in a camera generally desig nated by the numeral 60. Camera 60includes lens assembly 62, shutter assembly 10, and vidicon assembly 64.Vidicon assembly 64, the construction and operation of which areconventional and well known in the art, includes yoke 66.

The electrical connections of solenoids 16 and 17 are shownschematically at 68. The solenoids 16 and 17 are operatively connected,along with vidicon assembly 64, to control means 70 which is made in aconventional manner and serves the purpose of actuating the solenoids 16and 17 to produce an exposure while controlling the vidicon assembly torecord the image which is produced at the focal plane of lens assembly62. The image thus recorded by vidicon assembly 64 can be transmitted toa remote location by conventional electronic means. It should be notedthat when shutter assembly 10 is mounted in camera 60, pin 30 is seatedin a suitable bushing such as one fabricated of polyurethane in order tominimize microphonic effects on the vidicon assembly 64.

In operation, control means 70 actuates direct solenoid 17 which thenmoves direct blade 20 through arm 32 and link 34. When direct solenoid17 is actuated, direct blade 20 begins its movement downwardly therebybeginning to open aperture 26 to produce the exposure. After apre-determined interval, for example, 4, 8, or 16 milliseconds, afterpower is applied to direct solenoid 17, indirect solenoid 16 is actuatedthereby moving indirect blade 22 by means of arm 40 and link 42. Thismovement of indirect blade 22 begins to close the aperture. The bladespeed and power timing are such-that the two blades 20 and move acrossthe aperture 26 in a manner to create a moving slit across the same. Thechoice of the differential inpower timing, such as 4, 8, or 16milliseconds, will result in differing widths of the moving slit, with ahigher time differential creating the wider slit. Thus, the exposure isdetermined by the size of the slit.

It will be obvious to one of ordinary skill in the art thatthe'possibility exists in a shutter of the type described above that atthe end of the stroke of the blades there will be a bounce or rebound ofone or both of the blades thereby producing vibration and/or doubleexposure. Accordingly, in another aspect of the present invention, meansare provided for eliminating such a possibility, such means taking theform of a particular modification of the rotary solenoids to accomplishthis result. In this regard, attention is directed to FIGS. 9 through 12wherein the construction of the rotary solenoids is shown. It should beapparent that this construction is identical for both solenoids 16 and17. Thus, for purposes of this discussion, the solenoid is generallydesignated by the numeral 72. The rotary solenoid assembly 72 basicallyconsists of an armature 74, core 76, stator 78, and output shaft 80.Output shaft is fixed to armature 74 which is constructed so as to havea pair of opposed chordal lands" or flats 82. Drive arm 84 is secured tooutput shaft 80 and, in turn, is operatively connected to one of theblades 20 or 22 by means of a link. Stator 78 has a pair of tabs 86projecting outwardly, each of the tabs 86 having a width x.

A damper assembly 88 is provided, the damper assembly including a heavymetal ring 90 and a stop plate 92 made of Delrin which is apolyoxymethylene thermoplastic polymer made by the polymerization offormaldehyde and being hard, rigid, strong, tough and resilient as wellas being dimensionally stable. Of course, the stop plate can befabricated of any material having the properties of Delrin. The stopplate 92 has a pair of opposed slots 94 corresponding to tabs 86 whichwill fit thereinto and having a width of 0.020 inch greater than x. Thestop plate 92 is secured to the heavy metal ring 90 by any suitablemeans such as rivets 96.

Particular characteristics of the damper assembly 88 are that theinertia of theassembly is matched with that of the rest of thearmature-linkage-blade system in approximate ratio of l to 2 and itpermits the damper assembly 88 to rotate beyond the point of initialimpact by approximately 0.020 inch peripherally. It will be recognizedthat the impact referred to is that of the armature 74 against annaturestroke limiting stop 98 of stop plate 92.

The combination of the sized inertia and the amount of over travelpresent a controlled multiple collision reaction of the armature-bladesystem against the stop plate which reduces the coefficient ofrestitution in the system and consequently significantly reduces thebounce at the end of the stroke and, therefore, eliminates doubleexposure.

The mechanism of the multiple collision stop plate can be illustrated bythe simple analog of two colliding elastic balls and a fixed stop plate.Consider two balls of mass M and m travelling at speeds U and 14respectively along their line of centers with U u.

v u Damper mass e mass Stop After collision the velocities of the twoballs are V and v where, from the conservation of momentum For exampleif the second (damper) mass is half the primary mass, and is initiallyat rest then for a coefficient of restitution of V; we have m M/2, u=o,Fl

so that V, U/2 and v, U The damper mass then moves ahead and hits theend stop and is reflected with speed e x incident i.e. U/2.

A second collision between the masses occurs with ini-,

tial speeds of U/2 and U/2 resulting in post-collision speeds of Thedamper mass then strikes the stop plate for the second time and isreflected with speed U/4. Finally the damper mass hits the main mass forthe third collision resulting in speeds so that the damper mass comes torest and the main mass is reflected after these multiple collisions with/8 of its incoming speed. A single collision with a fixed stop platewould give return speed of k the incident speed so that the multiplecollision bumper is four times as effective in reducing the returnspeed.

The measured inertia of the Delrin and heavy metal stop plate wasapproximately half that of the rest of the system and a coefficient ofrestitution of 0.5 for Delrinto-steel collisions is typical. In thesimple example provided, the collisions have been assumed to beinstantaneous. In real life the finite time taken by the collisions mustof course be taken into account and they do lead to less reduction invelocity, however the simple example cited is illustrative of the methodof energy dissipation.

Actuation of each rotary solenoid produces a 65 rotation of the shaft aslimited by the internal stop plate. The 65 rotation, via the arm andlink, produces a linear motion of the specific blade associated withthat solenoid. Thus, using the device of the instant invention auniformity of exposure across the aperture and a repeatability ofexposure have been achieved both of which are within 0.4 millisecondover a temperature range of 0 C to 50 C. This performance is achievablefor a life of 1 million cycles in a vacuum of 10 torr. The shutterassembly will maintain this accuracy for any exposure time from 4 to 16milliseconds with simple adjustment of the input electrical pulses tothe direct and indirect solenoids. This shutter assembly also can beused as a means for rapid insertion and retraction of lens filters oncameras and can .be applied in such a way as to provide a relativelyhigh number of filters within a reasonably small package. The filterswould merely replace the shutter blades and would be drivenand held oncommand through rotary solenoids designed for continuous duty.Furthermore, the device can be used to produce a variety of shutterexposure times over a wider range by adjustment of solenoid torque,solenoid pulse timing, linkage ratios, blade to aperture sizing anddegrees of solenoid stroke.

It should be apparent from the foregoing detailed description that theobjects set forth hereinabove have been successfully achieved. Moreover,while there is shown and described a present preferred embodiment of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practisedwithin the scope of the following claims. Accordingly,

What is claimed is:

l. A camera shutter assembly comprising a pair of superposed opaqueplanar shutter blade members, each said member having aperture meanstherein and being arranged for reciprocal linear movement between aninitial rest position and a final rest position; a pair of rotarysolenoids, each of said solenoids being operatively connected to one ofsaid blade members by linkage means to cause movement of said blademembers when said solenoids are actuated; and means for actuating saidsolenoids such that one of said solenoids is actuated at a predeterminedtime interval before the other of said solenoids, whereby predeterminedportions of said aperture means coincide for a predetermined period oftime to permit the passage of incident radiation.

2. A shutter assembly defined in claim 1, wherein said predeterminedtime interval ranges from about 4 to 16 milliseconds.

3. A shutter assembly as defined in claim 1, wherein each of saidsolenoids comprises a core, stator means having a pair of opposed armsand at least partially surrounding said core, armature means having apair of opposed chordal lands, and substantially fixed damper means,said damper means comprising a heavy metal ring and a stop plate, saidstop plate having a pair of opposed armature limiting stops,. one ofsaid linkage means being fixed to said armature means through an outletshaft, said damper means having an inertia equal to one-half the inertiaof said armature means, said one of said linkage means, and acorresponding blade member.

4. A shutter assembly as defined in claim 3, wherein said stop plate isfabricated of a material having the characteristics of apolyoxymethylene thermoplastic polymer made by the polymerization offormaldehyde.

5. A shutter assembly as defined in claim 3, wherein each of said armsof said stator means has a tab extending therefrom and said stop plateincludes a pair of slots which mate with said tabs, said slots being0.020 inch wider than said tabs, whereby when said armature meansengages said stop plate, said stop plate will travel at most 0.020 inchfrom the impact.

6. A camera assembly comprising the shutter assembly of claim l, a lensassembly and a vidicon assembly,

said shutter assembly being interposed between said lens assembly andsaid vidicon assembly,

1. A camera shutter assembly comprising a pair of superposed opaqueplanar shutter blade members, each said member having aperture meanstherein and being arranged for reciprocal linear movement between aninitial rest position and a final rest position; a pair of rotarysolenoids, each of said solenoids being operatively connected to one ofsaid blade members by linkage means to cause movement of said blademembers when said solenoids are actuated; and means for actuating saidsolenoids such that one of said solenoids is actuated at a predeterminedtime interval before the other of said solenoids, whereby predeterminedportions of said aperture means coincide for a predetermined period oftime to permit the passage of incident radiation.
 2. A shutter assemblydefined in claim 1, wherein said predetermined time interval ranges fromabout 4 to 16 milliseconds.
 3. A shutter assembly as defined in claim 1,wherein each of said solenoids comprises a core, stator means having apair of opposed arms and at least partially surrounding said core,armature means having a pair of opposed chordal lands, and substantiallyfixed damper means, said damper means comprising a heavy metal ring anda stop plate, said stop plate having a pair of opposed armature limitingstops, one of said linkage means being fixed to said armature meansthrough an outlet shaft, said damper means having an inertia equal toone-half the inertia of said armature means, said one of said linkagemeans, and a corresponding blade member.
 4. A shutter assembly asdefined in claim 3, wherein said stop plate is fabricated of a materialhaving the characteristics of a polyoxymethylene thermoplastic polymermade by the polymerization of formaldehyde.
 5. A shutter assembly asdefined in claim 3, wherein each of said arms of said stator means has atab extending therefrom and said stop plate includes a pair of slotswhich mate with said tabs, said slots being 0.020 inch wider than saidtabs, whereby when said armature means engages said stop plate, saidstop plate will travel at most 0.020 inch from the impact.
 6. A cameraassembly comprising the shutter assembly of claim 1, a lens assembly anda vidicon assembly, said shutter assembly being interposed between saidlens assembly and said vidicon assembly.